Do I need class elements in persistence xml

Question

I have very simple persistance xml file    lt  xml version  1 0  encoding  UTF-8   gt   lt persistence version  1 0      xmlns  http   java sun com xml ns persistence  xmlns xsi  http   www w3 org 2001 XMLSchema-instance      xsi schemaLocation  http   java sun com xml ns persistence http   java sun com xml ns persistence persistence 1 0 xsd  gt        lt persistence-unit name  eventractor  transaction-type  RESOURCE LOCAL  gt           lt class gt pl michalmech eventractor domain User lt  class gt           lt class gt pl michalmech eventractor domain Address lt  class gt           lt class gt pl michalmech eventractor domain City lt  class gt           lt class gt pl michalmech eventractor domain Country lt  class gt            lt properties gt               lt property name  hibernate hbm2ddl auto  value  validate    gt               lt property name  hibernate show sql  value  true    gt           lt  properties gt       lt  persistence-unit gt    lt  persistence gt    and it works   But when I remove  lt class gt  elements application doesn t see entities  all classes are annotated with  Entity    Is there any automatic mechanism to scan for  Entity classes

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Not sure if you re doing something similar to what I am doing  but Im generating a load of source java from an XSD using JAXB in a seperate component using Maven  Lets say this artifact is called  base-model   I wanted to import this artifact containing the java source and run hibernate over all classes in my  base-model  artifact jar and not specify each  explicitly  Im adding  base-model  as a dependency for my hibernate component but the trouble is the  tag in persistence xml only allows you to specify absolute paths    The way I got round it is to copy my  base-model  jar dependency explictly to my target dir and also strip the version of it  So whereas if I build my  base-model  artifact it generate  base-model-1 0-SNAPSHOT jar   the copy-resources step copies it as  base-model jar     So in your pom for the hibernate component                lt  -- We want to copy across all our artifacts containing java code         generated from our scheams  We copy them across and strip the version         so that our persistence xml can reference them directly in the tag          lt jar-file gt target dependency   artifactId  jar lt  jar-file gt  -- gt           lt plugin gt               lt groupId gt org apache maven plugins lt  groupId gt               lt artifactId gt maven-dependency-plugin lt  artifactId gt               lt version gt 2 5 1 lt  version gt               lt executions gt                   lt execution gt                       lt id gt copy-dependencies lt  id gt                       lt phase gt process-resources lt  phase gt                       lt goals gt                           lt goal gt copy-dependencies lt  goal gt                       lt  goals gt                   lt  execution gt               lt  executions gt                      lt configuration gt                   lt includeArtifactIds gt base-model lt  includeArtifactIds gt                   lt stripVersion gt true lt  stripVersion gt               lt  configuration gt                   lt  plugin gt    Then I call the hibernate plugin in the next phase  process-classes                 lt  -- Generate the schema DDL -- gt           lt plugin gt               lt groupId gt org codehaus mojo lt  groupId gt               lt artifactId gt hibernate3-maven-plugin lt  artifactId gt               lt version gt 2 2 lt  version gt                lt executions gt                   lt execution gt                       lt id gt generate-ddl lt  id gt                       lt phase gt process-classes lt  phase gt                       lt goals gt                           lt goal gt hbm2ddl lt  goal gt                       lt  goals gt                   lt  execution gt               lt  executions gt               lt configuration gt                   lt components gt                       lt component gt                           lt name gt hbm2java lt  name gt                           lt implementation gt annotationconfiguration lt  implementation gt                           lt outputDirectory gt  src main java lt  outputDirectory gt                       lt  component gt                   lt  components gt                   lt componentProperties gt                       lt persistenceunit gt mysql lt  persistenceunit gt                       lt implementation gt jpaconfiguration lt  implementation gt                       lt create gt true lt  create gt                       lt export gt false lt  export gt                       lt drop gt true lt  drop gt                       lt outputfilename gt mysql-schema sql lt  outputfilename gt                   lt  componentProperties gt               lt  configuration gt           lt  plugin gt    and finally in my persistence xml I can explicitly set the location of the jar thus    lt jar-file gt target dependency base-model jar lt  jar-file gt    and add the property    lt property name  hibernate archive autodetection  value  class  hbm   gt

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For those running JPA in Spring  from version 3 1 onwards  you can set packagesToScan property under LocalContainerEntityManagerFactoryBean and get rid of persistence xml altogether   Here s the low-down

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You can provide for jar-file element path to a folder with compiled classes  For example I added something like that when I prepared persistence xml to some integration tests     lt jar-file gt file    target classes lt  jar-file gt

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for JPA 2  this does the trick    lt jar-file gt  lt  jar-file gt    scan all jars in war for annotated  Entity classes

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In Java SE environment  by specification you have to specify all classes as you have done      A list of all named managed persistence classes must be specified in Java SE environments to insure portability   and     If it is not intended that the annotated persistence classes contained in the root of the persistence unit be included in the persistence unit  the exclude-unlisted-classes element should be used  The exclude-unlisted-classes element is not intended for use in Java SE environments     JSR-000220 6 2 1 6   In Java EE environments  you do not have to do this as the provider scans for annotations for you    Unofficially  you can try to set  lt exclude-unlisted-classes gt false lt  exclude-unlisted-classes gt  in your persistence xml  This parameter defaults to false in EE and truein SE  Both EclipseLink and Toplink supports this as far I can tell  But you should not rely on it working in SE  according to spec  as stated above   You can TRY the following  may or may not work in SE-environments     lt persistence-unit name  eventractor  transaction-type  RESOURCE LOCAL  gt        lt exclude-unlisted-classes gt false lt  exclude-unlisted-classes gt        lt properties gt               lt property name  hibernate hbm2ddl auto  value  validate    gt               lt property name  hibernate show sql  value  true    gt       lt  properties gt   lt  persistence-unit gt

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Do I need Class elements in persistence xml    No  you don t necessarily  Here is how you do it in Eclipse  Kepler tested    Right click on the project  click Properties  select JPA  in the Persistence class management tick Discover annotated classes automatically

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The persistence xml has a jar-file that you can use  From the Java EE  5 tutorial    lt persistence gt       lt persistence-unit name  quot OrderManagement quot  gt           lt description gt This unit manages orders and customers              It does not rely on any vendor-specific features and can             therefore be deployed to any persistence provider           lt  description gt           lt jta-data-source gt jdbc MyOrderDB lt  jta-data-source gt           lt jar-file gt MyOrderApp jar lt  jar-file gt           lt class gt com widgets Order lt  class gt           lt class gt com widgets Customer lt  class gt       lt  persistence-unit gt   lt  persistence gt    This file defines a persistence unit named OrderManagement  which uses a JTA-aware data source jdbc MyOrderDB  The jar-file and class elements specify managed persistence classes  entity classes  embeddable classes  and mapped superclasses  The jar-file element specifies JAR files that are visible to the packaged persistence unit that contain managed persistence classes  while the class element explicitly names managed persistence classes  In the case of Hibernate  have a look at the Chapter2  Setup and configuration too for more details  EDIT  Actually  If you don t mind not being spec compliant  Hibernate supports auto-detection even in Java SE  To do so  add the hibernate archive autodetection property   lt persistence-unit name  quot eventractor quot  transaction-type  quot RESOURCE LOCAL quot  gt     lt  -- This is required to be spec compliant  Hibernate however supports        auto-detection even in JSE     lt class gt pl michalmech eventractor domain User lt  class gt     lt class gt pl michalmech eventractor domain Address lt  class gt     lt class gt pl michalmech eventractor domain City lt  class gt     lt class gt pl michalmech eventractor domain Country lt  class gt     -- gt      lt properties gt       lt  -- Scan for annotated classes and Hibernate mapping XML files -- gt       lt property name  quot hibernate archive autodetection quot  value  quot class  hbm quot   gt        lt property name  quot hibernate hbm2ddl auto quot  value  quot validate quot    gt       lt property name  quot hibernate show sql quot  value  quot true quot    gt     lt  properties gt   lt  persistence-unit gt

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Hibernate doesn t support  lt exclude-unlisted-classes gt false lt  exclude-unlisted-classes gt  under SE   another poster mentioned this works with TopLink and EclipseLink     There are tools that will auto-generate the list of classes to persistence xml e g  the Import Database Schema wizard in IntelliJ  Once you ve got your project s initial classes in persistence xml it should be simple to add remove single classes by hand as your project progresses

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Not necessarily in all cases   I m using Jboss 7 0 8 and Eclipselink 2 7 0  In my case to load entities without adding the same in persistence xml  I added the following system property in Jboss Standalone XML    lt property name  eclipselink archive factory  value  org jipijapa eclipselink JBossArchiveFactoryImpl   gt

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It s not a solution but a hint for those using Spring   I tried to use org springframework orm jpa LocalContainerEntityManagerFactoryBean with setting persistenceXmlLocation but with this I had to provide the  lt class gt  elements  even if the persistenceXmlLocation just pointed to META-INF persistence xml    When not using persistenceXmlLocation I could omit these  lt class gt  elements

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I m not sure this solution is under the spec but I think I can share for others   dependency tree  my-entities jar  Contains entity classes only  No META-INF persistence xml   my-services jar  Depends on my-entities  Contains EJBs only   my-resources jar  Depends on my-services  Contains resource classes and META-INF persistence xml   problems   How can we specify  lt jar-file  gt  element in my-resources as the version-postfixed artifact name of a transient dependency  How can we sync the  lt jar-file  gt  element s value and the actual transient dependency s one    solution  direct  redundant   dependency and resource filtering  I put a property and a dependency in my-resources pom xml    lt properties gt     lt my-entities version gt x y z-SNAPSHOT lt  my-entities version gt   lt  properties gt   lt dependencies gt     lt dependency gt       lt  -- this is actually a transitive dependency -- gt       lt groupId gt     lt  groupId gt       lt artifactId gt my-entities lt  artifactId gt       lt version gt   my-entities version  lt  version gt       lt scope gt compile lt  scope gt   lt  -- other values won t work -- gt     lt  dependency gt     lt dependency gt       lt groupId gt     lt  groupId gt       lt artifactId gt my-services lt  artifactId gt       lt version gt some very sepecific lt  version gt       lt scope gt compile lt  scope gt     lt  dependency gt   lt dependencies gt    Now get the persistence xml ready for being filtered   lt  xml version  1 0  encoding  UTF-8   gt   lt persistence     gt     lt persistence-unit name  myPU  transaction-type  JTA  gt               lt jar-file gt lib my-entities-  my-entities version  jar lt  jar-file gt             lt  persistence-unit gt   lt  persistence gt    Maven Enforcer Plugin  With the dependencyConvergence rule  we can assure that the my-entities  version is same in both direct and transitive    lt plugin gt     lt groupId gt org apache maven plugins lt  groupId gt     lt artifactId gt maven-enforcer-plugin lt  artifactId gt     lt version gt 1 4 1 lt  version gt     lt executions gt       lt execution gt         lt id gt enforce lt  id gt         lt configuration gt           lt rules gt              lt dependencyConvergence  gt           lt  rules gt         lt  configuration gt         lt goals gt           lt goal gt enforce lt  goal gt         lt  goals gt       lt  execution gt     lt  executions gt   lt  plugin gt

[java] Do I need <class> elements in persistence.xml?

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